What was the purpose of NATO when it was formed?

The primary purpose of NATO, formed in 1949, was to provide mutual defense against the threat of Soviet aggression during the Cold War era. The organization was established in response to the increasing tensions between Western nations and the Soviet Union, which were marked by territorial expansion and the establishment of communist governments in Eastern Europe. By creating a collective defense pact, NATO ensured that an armed attack against one member would be considered an attack against all, thereby deterring Soviet military aggression.

The focus on mutual defense was vital for the nations involved, as it aimed to promote stability and security in Western Europe at a time when the threat from the Soviet Union was prevalent. This mutual defense pact was rooted in the principle of collective security, a foundational idea that underpins NATO's activities even today. The other options, such as fostering economic cooperation, promoting democracy, or controlling nuclear proliferation, do align with various activities or goals of NATO or other organizations but do not capture the immediate and primary purpose of NATO's formation. Therefore, the designation of mutual defense against Soviet aggression as NATO's purpose is historically accurate and reflects the geopolitical context in which NATO was established.